Nature - Life


Although there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life is characterized by organization, metabolism, growth, adaptation, response to stimuli and reproduction. Life may also be said to be simply the characteristic state of organisms.

Properties common to terrestrial organisms (plants, animals, fungi, protists, archaea and bacteria) are that they are cellular, carbon-and-water-based with complex organization, having a metabolism, a capacity to grow, respond to stimuli, and reproduce. An entity with these properties is generally considered life. However, not every definition of life considers all of these properties to be essential. Human-made analogs of life may also be considered to be life.

The biosphere is the part of Earth's outer shell – including land, surface rocks, water, air and the atmosphere – within which life occurs, and which biotic processes in turn alter or transform. From the broadest geophysiological point of view, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere (rocks), hydrosphere (water), and atmosphere (air). Currently the entire Earth contains over 75 billion tons (150 trillion pounds or about 6.8 x 1013 kilograms) of biomass (life), which lives within various environments within the biosphere.

Over nine-tenths of the total biomass on Earth is plant life, on which animal life depends very heavily for its existence. More than 2 million species of plant and animal life have been identified to date, and estimates of the actual number of existing species range from several million to well over 50 million. The number of individual species of life is constantly in some degree of flux, with new species appearing and others ceasing to exist on a continual basis. The total number of species is presently in rapid decline.

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Other articles related to "life":

Widukind - Life
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Ecology - Relation To The Environment
... interlinked, and contains resources for organisms at any time throughout their life cycle ... internal environments, however, is an abstraction parsing life and environment into units or facts that are inseparable in reality ... There is an interpenetration of cause and effect between the environment and life ...
Half-life in Biology and Pharmacology
... A biological half-life or elimination half-life is the time it takes for a substance (drug, radioactive nuclide, or other) to lose one-half of its ... In a medical context, the half-life may also describe the time that it takes for the concentration in blood plasma of a substance to reach one-half of its steady-state value (the "plasma ... For example, the biological half-life of water in a human being is about seven to 14 days, though this can be altered by his/her behavior ...
Faith in Other Spiritual Traditions - Meher Baba
... kinds of faith (i) faith in oneself, (ii) faith in the Master and (iii) faith in life ... Faith is so indispensable to life that unless it is present in some degree, life itself would be impossible ... It is because of faith that cooperative and social life becomes possible ...
International Space Station - Station Systems - Life Support
... The Russian orbital segment's life support systems are contained in the Service Module Zvezda ... The MLM Nauka laboratory has a complete set of life support systems ...

Famous quotes containing the word life:

    Life is the desert, life the solitude,
    Death joins us to the great majority.
    Edward Young (1683–1765)

    As life developed, I faced each problem as it came along. As my activities and work broadened and reached out, I never tried to shirk. I tried never to evade an issue. When I found I had something to do—I just did it.
    Eleanor Roosevelt (1884–1962)

    “O life of this our Spring! why fades the lotus of the water?
    Why fade these children of the Spring,born but to smile and fall?
    William Blake (1757–1827)